1. Field of the Invention
The present invention relates to a double-action mechanical press capable of upward and downward movement an upper ram and a lower ram while both movements are related each other by a common driving source.
2. Related Art
As an example, a double-action mechanical press has been used to shape a blank into a cup-like configuration and then draw the bottom of the cup-shaped material while holding the position of the upper flange of the cup-shaped material in the upward and downward directions to form a cylindrical-shape of a beverage can.
For example, Japanese Patent Application Laid-Open No. 9-285897 discloses a conventional double-action mechanical press which comprises an upper ram continuously movable in the upward and downward directions and a lower ram associated with the upper ram to stop at a given position for a given time period, as show in FIG. 8.
This conventional double-action mechanical press has two drive linkage mechanisms disposed on the both sides of a frame. These two drive linkage mechanisms can be rotated by a single crankshaft in the forward and backward directions of the frame at its central position. Each of the drive linkage mechanisms includes an upper link for driving upward and downward the upper ram and a lower link for driving upward and downward the lower ram.
In such a double-action mechanical press of the conventional art, however, it is very difficult to keep its dynamic balance since large components force in a forward and backward directions exert onto the two drive linkage mechanisms. The both rams are moved upward and downward by the two drive linkage mechanisms at the central position of the frame extending forward and backward. To maintain the parallelism (or horizontal degree) of each ram, thus, 4 guideposts for the ram need to be strong. In addition, it is necessary that the drive linkage mechanism keeps the whole dynamic balance including the dynamic balances of both the rams in their forward and backward directions. Thus, the drive linkage mechanisms must be connected to other linkage mechanisms exclusive for the dynamic balance. This tends to make the double-action mechanical press complicated and upsized. Furthermore, the balance weight must be increased. In general, it is difficult to improve the stroke per minute (SPM) and accuracy of finishing.
In the conventional press, the respective mechanisms themselves in the press must be modified or adjusted to change the slide stroke diagram of the lower ram. The adjustment of die height must carefully be performed through a complicated operation while the operation of the press is stopping, since it should be set by a die-height adjusting device incorporated into the slide section of the press. Since the die-height adjusting device itself incorporated into the slide section of the press becomes a load on the driving source, the press will have no choice but to upsize.
It is thus an objective of the present invention to provide a double-action mechanical press of such a simplified structure that can easily keep the dynamic balance and that can ensure an improved SPM and accuracy of finishing by maintaining the parallelism in each ram.
Another objective of the present invention is to provide a double-action mechanical press which can disperse a load corresponding to the reaction force from the lower ram toward the driving source and which can simplify the supporting structure of the lower ram to reduce the manufacturing cost.
Still another objective of the present invention is to provide a double-action mechanical press which can adjust the die height and also change the slide stroke in the lower ram with no modification to the mechanism and without provision of any load onto the driving source.
In one aspect, the present invention provides a double-action mechanical press comprising:
a driving source;
a crank mechanism driven by the driving source, the crank mechanism including a crankshaft which has two of first eccentric sections and two of second eccentric sections;
an upper ram being moved upward and downward by the power from the first eccentric sections;
a lower ram being moved upward and downward by the power from the second eccentric sections;
a plurality of upright rods for transmitting the power from each of the second eccentric sections in the crank mechanism; and
two toggle linkage mechanisms each of which rotates in the opposite direction from each other in a vertical plane by the power inputted through the plurality of upright rods to move the lower ram in the upward and downward directions.
For example, if the crank mechanism, in a crown is driven according to this aspect of the present invention, the upper ram connected to the first eccentric sections which are spaced rightward and leftward, for example, through connecting rods or the like can be moved upward and downward. This crank mechanism will not cause any unbalance in the rightward and leftward directions. Since it is only required to keep the rotational balance, therefore, the structure of keeping the dynamic balance will be simpler.
The second eccentric sections in the crank mechanism moves the lower ram upward and downward by rotating the toggle linkage mechanisms oppositely from each other in the rightward and leftward directions in a bed through the upright rods. At this time, the upper position of the lower ram may be its retention position. Since each of the toggle linkage mechanisms are oppositely rotated from each other in the rightward and leftward directions, the parallelism in the lower ram can be maintained without making the guideposts more rugged.
In other words, the dynamic components in the rightward and leftward directions may be counteracted by each other since two toggle linkage mechanisms which are spaced rightward and leftward are oppositely rotated in the rightward and leftward directions. Each of the toggle linkage mechanisms will be simplified in structure since only the dynamic balance in the upward and downward moving member may be kept. In such a manner, the present invention can provide a double-action mechanical press of such a simplified structure that can easily keep the dynamic balance and that can ensure an improved SPM and accuracy of finishing by maintaining the parallelism in each ram.
In this aspect, the driving source may include a pair of driving sources for applying a rotational force onto both ends of the crankshaft. Thus, the pair of driving sources can function as a dual-system brake to more improve the safety and rightward and leftward balance.
The crankshaft may further include two of third eccentric sections for driving balance weights. In such a case, a rotational phase difference may be provided between the first eccentric sections and the second eccentric sections. At this time it is preferable that the third eccentric sections are disposed at positions (Pe) opposite to eccentric positions (Pc) about the crankshaft, the eccentric positions (Pc) being composition of masses of eccentric positions (Pa) of the first eccentric sections and eccentric positions (Pb) of the second eccentric sections.
Thus, the rotational balance in the crankshaft can be kept even if any phase difference is provided between the upper and lower rams when driven.
According to this aspect of the present invention, the lower ram being moved upward and downward may be retained at its upper position.
In another aspect, the present invention provides a double-action mechanical press comprising:
a driving source;
two crank mechanisms driven by the driving source, each of the crank mechanisms including a crankshaft which has a first eccentric section and a second eccentric section;
a plurality of upright rods for transmitting the power from the second eccentric section of each of the crank mechanisms;
an upper ram being moved upward and downward by the power from the plurality of upright rods;
a lower ram being moved upward and downward by the power from the second eccentric section of each of the crank mechanisms; and
two toggle linkage mechanisms receiving the power from the second eccentric section of each of the crank mechanisms and rotating in the opposite direction from each other in a vertical plane to move the lower ram in the upward and downward directions.
When both the crank mechanisms are rotated through main gear or the like, the upper ram is moved upward and downward by the respective first eccentric sections, for example, through the upper-ram-driving connecting rods and upright rods. Such an upward and downward movement of the upper ram will not produce any unbalance in the rightward and leftward directions. Therefore, the dynamic balance can perfectly be kept, for example, by mounting a balance weight on the main gear.
Since each of the toggle linkage mechanisms are oppositely rotated from each other in the rightward and leftward directions by the second eccentric sections driven at the same time of the above motion, the toggle linkage mechanisms can move the lower ram upward and downward. At this time, the upper position of the lower ram may be its retention position.
Since the toggle linkage mechanisms which are spaced rightward and leftward are oppositely rotated in the rightward and leftward directions, the dynamic components in the rightward and leftward (or horizontal) directions can be counteracted by each other. In other words, the dynamic balance in the upward and downward directions may also be kept in the lower ram. For example, a balance weight may simply be mounted on each of the toggle linkage mechanisms opposite to the connection portion to the lower-ram-driving connecting rods.
This aspect of the present invention can also provide a double-action mechanical press of such a simplified structure that can easily keep the dynamic balance and that can ensure an improved SPM and accuracy of finishing by maintaining the parallelism in each ram. Unlike the first mentioned aspect, this aspect can eliminate a crown on the upper part of the machine. Therefore, the press can be downsized. And also, the lubricating oil will not leak onto the pressed products. In addition, the oil treating system may be simplified in structure.
The driving source may include a pair of driving sources each for applying a rotational power to each of the crankshafts, one of the pair of driving sources applying a rotational power to one of the crankshafts, and the other one of the pair of driving sources applying a rotational power to the other one of crankshafts. In this case, it is preferable each of the crankshafts includes two pinion gears fixedly mounted thereon at both ends. Thus, two pinion gears fixed at one end of each of the crankshafts may mesh each other while other two pinion gears fixed at the other end of each of the crankshafts mesh each other. As a result, the pair of driving sources will function as a double-system brake to more improve the safety and rightward and leftward balance.
It is preferable that the toggle linkage mechanisms have two main gears meshing the pinion gears fixedly mounted on the crankshafts, and that each of the main gears includes a balance weight fixedly mounted thereon.
When two main gears rotated in the opposite directions from each other include balance weights fixedly mounted thereon, all the mass balances in the upper and lower rams moved upward and downward for a sine curve (STU) as shown in FIG. 13 can be kept.
It is further preferable that each of the toggle linkage mechanisms has a balance weight.
According to this aspect, the dynamic components in the rightward and leftward (or horizontal) directions may be counteracted by each other since the toggle linkage mechanisms are rotated oppositely from each other. This can provide an extremely simplified structure only by mounting balance weights for keeping the balance in the upward and downward directions in the lower ram or the like on the two toggle linkage mechanisms.
Even in this embodiment of the present invention, the lower ram being moved upward and downward is retained at the upper position thereof.
In a further aspect of the present invention, two toggle linkage mechanisms of the double-action mechanical press may comprise a common toggle point shaft.
Since the system span can be reduced in any small-sized press producing fewer products, two toggle linkage mechanisms can be disposed making a toggle point shaft in common. When the two toggle linkage mechanisms are oppositely rotated from each other about the common toggle point shaft in the rightward and leftward directions, the dynamic components in the rightward and leftward (or horizontal) directions can surely be counteracted by each other.
Preferably, each of the toggle linkage mechanisms comprises: a swing arm swinging about the common toggle point shaft as a fulcrum; a lower-ram-driving connecting rod connecting between the second eccentric section and the swing arm; and a connecting link connecting the lower ram and the swing arm, and the swing arm, the lower-ram-driving connecting rod and the connecting link substantially form an inverted Y-shaped configuration.
Thus, a reaction force F corresponding to the load from the lower ram can be dispersed into components F1 and F2 toward the driving source, as shown in FIG. 14. At the same time, the pressing operation can be accelerated by rotating the second eccentric sections at an increased speed.
It is further preferable that the double-action mechanical press comprises mechanism for adjusting the upward and downward positions of the common toggle point shaft.
Thus, the die height, lower ram motion and slide stroke can be changed by adjusting the upward and downward positions of the common toggle point shaft relative to the two toggle linkage mechanisms.